We report on neodymium doped LaF3 nanoparticles dispersed in a photo definable polymer. Standard spin coating is used to deposit uniform thin films on a silicondioxide buffer layer, which can be photocured and developed to produce monomode active optical waveguides. Optical properties of the film are obtained using a prism coupling setup, showing low losses of the photosensitive polymer host material in both the visible and infrared. In addition, the absorption and emission due to the neodymium doped LaF3 nanoparticles have been determined for a range of particle concentrations.